Mobile devices with various methods of connectivity are now for many people becoming the primary gateway to the internet and also a major storage point for personal information. This is in addition to the normal range of personal computers and furthermore sensor devices plus internet based providers. Combining these devices together and lately the applications and the information stored by those applications is a major challenge of interoperability. This can be achieved through numerous, individual and personal information spaces in which persons, groups of persons, etc. can place, share, interact and manipulate (or program devices to automatically perform the planning, interaction and manipulation of) webs of information with their own locally agreed semantics without necessarily conforming to an unobtainable, global whole.
Such distributed computing systems involve numerous information transactions among various distributed sources. In many occasions, information may be transferred, updated, inserted or deleted to and from multiple distributed information sources, while at the same time requests for information may be issued and processed at any location. In such occasions, consistency of information may become an issue. For example, if a request for information is received and processed at the same time as a deleting process for the same information is underway, the requester may receive an erroneous response to its request.